The Merc rebels are mostly former Mexican soldiers and hired mercenaries from Cuba. However, there are reports that Emiliano is recruiting foreign mercenaries from Africa and the Middle East. These African and Middle Eastern Mercs are mostly from countries with corrupt governments. So it only made sense for them to share in Emiliano's war against a regime he sees as corrupt. In return for their services, Emiliano promises these African and Middle Eastern recruits a "better world" once the war is won.